Adsorption-Driven Interfacial Engineering of Aluminum Anodes via Saponin for Enhanced Performance in Aluminum-Air Batteries

Herein, saponin, a low-cost and environmentally benign amphiphilic biosurfactant, is introduced into 4 M NaOH to regulate the Al anode interface through adsorption-driven interfacial engineering.

Experimental characterization and molecular simulations indicate that oxygen-containing groups in saponin interact with the Al surface through Al–O interactions, forming a saponin-derived adsorption layer. This interfacial layer limits the access of H₂O and OH^– to active Al sites, suppresses parasitic hydrogen evolution, and promotes more uniform anodic dissolution. At the optimal concentration of 15 mM, saponin achieves a corrosion inhibition efficiency of 58.9% and increases Al utilization from 47.8% to 79.4%.